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remotelocal 04-06-15 07:02 PM

Switching out 140mm fork for 160mm fork
Hi all, I realize there are variations on this question floating around, ut wondering if anyone has experience with the same or very similar frame to mine...

I've got a Kona Precept DL that I've basically replaced most parts on, and the last step is a better fork. ( the bike - KONA BIKES | 2015 BIKES | TRAIL DS | PRECEPT DL )

The headtube angle is 68degrees at the moment, and I'm seeing some good prices on 150mm and 160mm forks, and i'm just wondering what the deal and balance is here.

Will the geo be changed that much that it noticeably affects the ride, seat to cranks or anything like that? Is the extra 1-2cms of travel worth the hassle? Should I just fish around until I find a 140mm fork and stick with what it has geo-wise? I also notice the new 2016 fox 34 for 27.5 has a shorter crown to axle distance, so there's all sorts of variables here I guess? I'm looking at picking up a RS Pike or Fox Float Factory 34 depending on what I can find at a suitable price point.

thanks all.

dminor 04-07-15 11:13 AM

68 is pretty steep for the type of bike it is. Your Precept would benefit greatly from a degree or two slacker head tube angle. Depending on the axle-to-crown length of the replacement you're looking at, that is about what you will achieve. You will get conflicting advice here with a few people stuck in old-skool rule-of-thumb thinking on fork length; but the bike will easily handle it.

One caveat: If you are concerned about your frame warranty, you'd be well off to check with your shop and/or Kona to be sure going to the longer fork won't void the warranty.

ColinL 04-07-15 11:33 AM

I searched a bit and found that the axle-to-crown length on your current fork is 530mm. As a rule of thumb, if you make the fork no more than 20mm longer, handling won't be significantly changed.

Many current 150mm and 160mm forks can be lowered to 140mm and should have similar axle-to-crown length at 140mm travel. For example I'm on a Manitou Mattoc Expert which is 525mm a2c at 140mm travel (for my 26" version-- 27.5 would be 535mm). It's actually a 170mm fork with up to 3 travel spacers that can be installed to take it down to 140mm, and comes with 1 of them pre-installed to be 160mm. Some forks do still have to be permanently modified to shorten their travel but a lot have air / travel spacers like this. You might want to ride it at the stock length to start with and only lower it if you feel the handling has been negatively affected.

Figure out what fork you want based on features and price. If you know anyone with such a fork that you can ride, definitely try to get in a test-ride. But you might have to take a leap of faith. Here's the shortlist I'd work with:

Rockshox Pike - has both dual-position or solo air options - revolutionary 3 years ago, competitive today
Manitou Mattoc - easy to service and modify travel, hydraulic bottom-out, cheapest online price
MRP Stage - small company based out of Colorado but the fork has solid reviews, ramp control feature is unique
Fox 36 - expensive and possibly overkill
BOS Deville - heinously expensive and questionable parts / service availability in North America
Wait until late summer / early fall for New Fox 34 - pre-production test reports sound quite favorable

ColinL 04-07-15 11:39 AM

Also, this calculator can be used to see what will happen to your bike's geometry.

160mm fork would be almost exactly 1 deg slacker HT and ST angles, and about 7mm higher bottom bracket. That is no problem at all.

I should also mention, having done this myself, that when you get a much better fork on your bike you could possibly notice shortcomings with your shock and want/need to change it as well.

remotelocal 04-07-15 07:12 PM

thanks dminor and ColinL, this is exactly why I come here! Superb information and advice. thanks again!

slowride454 04-09-15 04:30 PM

how do you like the bike overall? I was thinking about going Kona Precept DL or Giant Stance vs the Process or Trance

remotelocal 04-10-15 05:56 PM

Hey Slowride, I can't claim to have a vast knowledge of mountainbikes to compare it to, but I've been completely over the moon with the precept dl. I went with the DL over the stock Precept, which in hindsight has only really benefited me in that I like orange more than green! The DL is specced better than the standard precept, but since I bought it, i've replace the brakes with XT levers/calipers, XTR ICE rotors, replaced the shifters with XT, put an XT shadow plus rear on it, switched to an XT 10spd cassette, replaced the crankset with SLX and left the front SLX shifter on it. I've also replaced the rear shock with a fox float factory, and as above am looking to now swap out the fork. so in reality, I coul have got here with the standard precept and the only difference would be that my bike was snot green.

As for the stuff that actually matters, riding it has been superb. I've been a road cyclist for far too many years, and a commuter as well, and i've made a hard switch to mountainbiking and couldn't be happier, so the precept happens to be the bike i'm on right now, so it can do no wrong! But i can hammer it up the hills, blast downhills, it absolutely rails through corners, feel super tight and stable, i'm jamming off jumps that make me feel like a kid on a BMX and it handles it all beautifully. It's wide barred like most, but it feels nimble and capable. The top tube length is short, but its that style of "all mountain" bike so thats normal i guess but damn its comfortable to spend all day on. I even commute on it. in short, I love it!

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